EP0491202A2 - Access method - Google Patents
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- Publication number
- EP0491202A2 EP0491202A2 EP91120531A EP91120531A EP0491202A2 EP 0491202 A2 EP0491202 A2 EP 0491202A2 EP 91120531 A EP91120531 A EP 91120531A EP 91120531 A EP91120531 A EP 91120531A EP 0491202 A2 EP0491202 A2 EP 0491202A2
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- Prior art keywords
- token
- packet
- channels
- station
- transmission
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/64—Hybrid switching systems
- H04L12/6418—Hybrid transport
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/12—Arrangements providing for calling or supervisory signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/40143—Bus networks involving priority mechanisms
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/407—Bus networks with decentralised control
- H04L12/417—Bus networks with decentralised control with deterministic access, e.g. token passing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/64—Hybrid switching systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/64—Hybrid switching systems
- H04L12/6418—Hybrid transport
- H04L2012/6445—Admission control
- H04L2012/6448—Medium Access Control [MAC]
- H04L2012/6451—Deterministic, e.g. Token, DQDB
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/64—Hybrid switching systems
- H04L12/6418—Hybrid transport
- H04L2012/6445—Admission control
- H04L2012/6459—Multiplexing, e.g. TDMA, CDMA
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/64—Hybrid switching systems
- H04L12/6418—Hybrid transport
- H04L2012/6464—Priority
Definitions
- the invention relates to a method for accessing time-division multiplex channels of a transmission system using tokens. Such methods and transmission systems that operate according to this access method are known.
- a method for controlling access to a time-division multiplex message transmission path of a transmission system in which in one time frame, some of the time slots are used as fixed channels, another part of the time slots are used for the transmission of data packets (bursts) and the remaining time slots are used for signaling purposes.
- the division of the time slots between the fixed channels and burst channels is variable.
- the transmission system contains several stations that can access the transmission path at the same time.
- the time slots which are provided for packet operation are accessed by the station in question sending a bit pattern on a signaling channel which has a certain priority.
- the station that sends the bit pattern with the highest priority is given access to the time slot.
- the probability of being able to access the time slots reserved for burst operation for each station depends not only on the priority but also on the length of the bursts sent. Assuming that all stations transmit on average with the same priority, the stations do not have calculable access times if the transmitted packet lengths vary widely. This can cause a buffer memory contained in a station to overflow and messages to be lost as a result of this station not being able to access a time slot in time.
- each station sends a token before the transmission of a packet in a signaling channel, which token contains a priority number and a packet length number which specifies the length of the packet to be transmitted, and only when its token is subsequently received sends the packet in the signaling channel, whereby each station determines the starting point for its own transmission from the details of the tokens contained in the signaling channels in one of the following time frames, in which it forms the sum of all packet lengths that are specified in the tokens that occur one in the time frame in front of your own token place.
- the station in the event that the token it sends out has been overwritten by another station with a higher priority, increases the priority number of its token by a certain value and then retransmits its token on a signaling channel.
- the value of the increase suitably corresponds to the number of other stations in the transmission system.
- the stations only send out a token if a free token is present in the signaling channel. If, on the other hand, a busy token is present in the signaling channel, the stations do not send any tokens, but wait until a free token is available in a subsequent frame.
- the free tokens and the occupied tokens are from one generated specific station of the transmission system, which evaluates the tokens contained in a frame considered. If the transmission capacity requested by these tokens is smaller than the maximum available in one frame, a free token is sent in the following frame. If the sum of the packet lengths defined by the tokens sent out in a particular frame is greater than the length of one or more frames, as many consecutive frames are provided with an occupied token as can be completely occupied due to the requested packet lengths and only in the following frame sent a free token.
- the time frame shown schematically in FIG. 1 contains 1088 channels with a length of 1088 bytes. Of these, 992 channels are available for the transmission of information and the remaining 96 channels are signaling channels.
- the first 32 signaling channels form the so-called system control block SCB, in which the control information necessary for the operation of the message transmission system is transmitted.
- a further four channels form a so-called token control block TCB, of which the first channel contains either an occupied token or a free token.
- the other three channels serve as runtime compensation.
- the remaining 60 channels form a so-called token block TB.
- a token has a length of 2 bytes and consists of a priority number PZ and a packet length number PL. The packet length is specified in units of 4 bytes.
- FIG. 2 shows a time frame, the channels of which are partially reserved for fixed-channel operation and partially intended for packet operation. It also contains the system control block SCB, the token control block TCB and the token block. Since the number of channels provided for packet operation is smaller than in the example according to FIG. 1, only correspondingly fewer signaling channels, namely 28, are provided for the token block.
- Each station of the transmission system is assigned a specific token location and a specific priority number.
- the priority numbers and token places are assigned so that different priority numbers are assigned to the stations to which the same token place is assigned.
- the priority numbers assigned to the stations can be the same if the stations have been assigned different token places.
- the priority assigned to a token of a station depends on the priority number and the token space assigned to the station.
- a certain station of the transmission system generates the busy and free tokens depending on the Sum of all packets to be transferred.
- a free token in a frame N signals to the stations that N tokens can be sent in the following token block of the frame.
- An occupied token indicates that there is no token block in the frame under consideration, but that all channels are used for the information transmission.
- the particular station adds up all the packet length numbers available in frame N. The sum of all packet length numbers results in the number of frames in which it must send out an occupied token. If the sum of all packet lengths is less than 992 bytes, it sends out a free token in the following frame N + 1.
- a station wants to transmit a message, it looks for a free token in the token control block. After recognizing a free token, it writes its priority number and the packet length of the message to be transmitted in the token space assigned to it. If other stations are assigned to the same token location, a token can already be located on this token location. If the token of the station in question has a higher priority number than the token of the other station, the station in question overwrites the other token. Otherwise, it waits for the next time frame. The station in question then checks whether its token has been overwritten by a third station. If it finds its token in the token block, it gets access to the transmission path.
- a station If a station has not received access to the transmission path because another station has overwritten its token, it increases its priority number by a certain amount and sends out its new token in one of the following frames.
- the amount of the increase is in the simplest case equal to the number of stations that have been allocated the same token space. Due to the amount and the allocation of a certain token space, each station can determine its access time deterministically. After receiving access, the priority number is reset to its original value.
- a station If a station has access to the transmission path, it can send out its packet in one of the next time frames.
- the station determines the starting point for this transmission from the packet lengths of the packets specified in the token block, which come from stations with a token slot located in front of its own.
- a package consists of a header, the actual information and data backup bits.
- the header begins with a start word and contains the recipient and sender address as well as the length of the information contained in the package.
- FIG. 3A shows a time frame N according to FIG. 1, the token control block of which contains a free token and the token block of which contains a token at the fourth, fifth, eleventh and thirtieth token positions.
- the station with the token place 4 specified the priority number 10 and the packet length number 74. This station has to transmit 74 x 4 bytes.
- the total number of information to be transmitted in this example is 656 bytes. Since the total of all packet lengths does not exceed the 992 bytes available in the next frame N + 1, a free token is again sent in the next frame in the token control block and a token block is provided.
- 3b the transmission of the first begins Packet in the first channel after the token block. The other packets immediately follow the previous packets. The rest of the frame N + 1 is not occupied.
- FIG. 4a shows, just like FIG. 3a, an example of a time frame N which contains a free token in the token control block and four tokens on four token locations in the token block.
- the frame N + 1 has a busy token after the system control block.
- the frame N + 1 does not contain a token block.
- the first packet begins immediately after the busy token, followed by the second packet (FIG. 4b).
- the part of the second packet that no longer finds space in frame N + 1 is transmitted in frame N + 2.
- the third and fourth packages follow the second package. Since frame N + 2 is not fully occupied, it contains a free token and a token block (FIG. 4c). Since no token is contained in the token block of frame N + 2, no information is transmitted at all in frame N + 3 (FIG. 4d).
- each station When receiving, each station compares the recipient address contained in the header of the packets with its own address. If the addresses match, the station stores the packet in a receive memory. The length of the packet is taken from the header and can thereby determine the end of the packet and the beginning of the next packet.
- the distribution of the time slots on fixed channels and channels used for the transmission of packets depends on the transmission capacity required in each case controlled. Corresponding control information is transmitted in the system control block.
- the time slots of a time frame can also be divided into several so-called subframes, each of which contains its own token control block, token block and a certain number of time slots for information transmission and are assigned to different groups of stations. This makes it possible to reserve transmission capacity for individual groups of stations even when the transmission path is heavily loaded.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Data Exchanges In Wide-Area Networks (AREA)
- Small-Scale Networks (AREA)
- Time-Division Multiplex Systems (AREA)
Abstract
Description
Die Erfindung bezieht sich auf ein Verfahren zum Zugreifen auf Zeitmultiplex-Kanäle eines Übertragungssystems mittels Token. Derartige Verfahren und Übertragungssysteme, die nach diesem Zugriffsverfahren arbeiten, sind bekannt.The invention relates to a method for accessing time-division multiplex channels of a transmission system using tokens. Such methods and transmission systems that operate according to this access method are known.
Aus der EP-A-0 115 883 ist ein Verfahren zum Steuern des Zugriffs auf einen Zeitmultiplex-Nachrichtenübertragungsweg eines Übertragungssystems bekannt, bei dem in einem Zeitrahmen ein Teil der Zeitschlitze als Festkanäle, ein anderer Teil der Zeitschlitze für die Übertragung von Datenpaketen (Bursts) und die restlichen Zeitschlitze für Signalisierzwecke verwendet werden. Die Aufteilung der Zeitschlitze zwischen den Festkanälen und Burst-Kanälen ist variabel. Das Übertragungssystem enthält mehrere Stationen, die auf den Übertragungsweg gleichzeitig zugreifen können.From EP-A-0 115 883 a method for controlling access to a time-division multiplex message transmission path of a transmission system is known, in which in one time frame, some of the time slots are used as fixed channels, another part of the time slots are used for the transmission of data packets (bursts) and the remaining time slots are used for signaling purposes. The division of the time slots between the fixed channels and burst channels is variable. The transmission system contains several stations that can access the transmission path at the same time.
Der Zugriff auf die Zeitschlitze, die für Paket-Betrieb vorgesehen sind, erfolgt dadurch, daß die betreffende Station auf einem Signalisierkanal ein Bitmuster aussendet, dem eine bestimmte Priorität zukommt. Den Zugriff auf den Zeitschlitz erhält die Station, die das Bitmuster mit der höchsten Priorität aussendet.The time slots which are provided for packet operation are accessed by the station in question sending a bit pattern on a signaling channel which has a certain priority. The station that sends the bit pattern with the highest priority is given access to the time slot.
Die Wahrscheinlichkeit für jede Station auf die für Burst-Betrieb reservierten Zeitschlitze zugreifen zu können, hängt jedoch nicht nur von der Priorität sondern auch von der Länge der gesendeten Bursts ab. Unter der Annahme, daß alle Station im Mittel mit derselben Priorität senden, ergibt sich dennoch für die Stationen dann keine kalkulierbaren Zugriffszeiten, wenn die gesendeten Paketlängen stark variieren. Dies kann dazu führen, daß ein in einer Station enthaltener Pufferspeicher überläuft, und dadurch Nachrichten verlorengehen, weil diese Station nicht rechtzeitig auf einen Zeitschlitz zugreifen konnte.The probability of being able to access the time slots reserved for burst operation for each station depends not only on the priority but also on the length of the bursts sent. Assuming that all stations transmit on average with the same priority, the stations do not have calculable access times if the transmitted packet lengths vary widely. This can cause a buffer memory contained in a station to overflow and messages to be lost as a result of this station not being able to access a time slot in time.
Es ist daher Aufgabe der Erfindung ein Verfahren zum Zugreifen auf einen für die Übertragung von Paketen verwendeten Kanal eines Zeitmultiplex-Systems anzugeben, das es jeder Station gestattet, innerhalb einer definierbaren Zugriffszeit auf den Kanal zuzugreifen.It is therefore an object of the invention to provide a method for accessing a channel of a time-division multiplex system used for the transmission of packets, which allows each station to access the channel within a definable access time.
Die Lösung dieser Aufgabe erfolgt erfindungsgemäß durch ein Verfahren, bei dem jede Station vor dem Senden eines Pakets in einem Signalisierkanal einen Token aussendet, der eine Prioritätszahl und eine Paketlängenzahl enthält, die die Länge des zu übertragenden Paketes angibt, und nur bei anschließendem Empfang ihres Tokens im Signalisierkanal das Paket sendet, wobei jede Station aus den Angaben der in den Signalisierkanälen enthaltenen Token den Startpunkt für ihre eigene Sendung in einem der folgenden Zeitrahmen ermittelt, in dem sie die Summe aller Paketlängen bildet, die in den Token angegeben sind, die sich auf einem im Zeitrahmen vor dem eigenen liegenden Token-Platz befinden.This object is achieved according to the invention by a method in which each station sends a token before the transmission of a packet in a signaling channel, which token contains a priority number and a packet length number which specifies the length of the packet to be transmitted, and only when its token is subsequently received sends the packet in the signaling channel, whereby each station determines the starting point for its own transmission from the details of the tokens contained in the signaling channels in one of the following time frames, in which it forms the sum of all packet lengths that are specified in the tokens that occur one in the time frame in front of your own token place.
Besonders vorteilhaft ist es, wenn die Station in dem Fall, daß der von ihr ausgesendete Token von einer anderen Station mit höherer Priorität überschrieben wurde, die Prioritätszahl ihres Tokens um einen bestimmten Wert erhöht, und danach ihren Token erneut auf einem Signalisierkanal aussendet. Der Wert der Erhöhung entspricht zweckmäßigerweise der Anzahl der anderen Stationen des Übertragungssystems. Ist schließlich ein Zugriff auf den Übertragungsweg erfolgt und wurde das Paket ausgesendet, wird die Prioritätszahl der betreffenden Station wieder auf den ursprünglichen Wert herabgesetzt.It is particularly advantageous if the station, in the event that the token it sends out has been overwritten by another station with a higher priority, increases the priority number of its token by a certain value and then retransmits its token on a signaling channel. The value of the increase suitably corresponds to the number of other stations in the transmission system. Once the transmission path has been accessed and the packet has been sent out, the priority number of the station in question is reduced again to the original value.
Die Stationen senden erfindungsgemäß nur dann einen Token aus, wenn im Signalisierkanal ein Frei-Token vorhanden ist. Ist im Signalisierkanal dagegen ein Belegt-Token vorhanden, senden die Stationen keine Token aus, sondern warten so lange, bis in einem nachfolgenden Rahmen ein Frei-Token vorhanden ist.According to the invention, the stations only send out a token if a free token is present in the signaling channel. If, on the other hand, a busy token is present in the signaling channel, the stations do not send any tokens, but wait until a free token is available in a subsequent frame.
Die Frei-Token und die Belegt-Token werden von einer bestimmten Station des Übertragungssystems generiert, die die in einem betrachteten Rahmen enthaltenen Token auswertet. Ist die durch diese Token angeforderte Übertragungskapazität kleiner als die maximale in einem Rahmen zur Verfügung stehende, so wird im folgenden Rahmen ein Frei-Token gesendet. Ist die Summe der von den in einem bestimmten Rahmen ausgesendeten Token definierten Paketlängen größer als die Länge eines oder mehrerer Rahmen, so werden so viele aufeinanderfolgender Rahmen mit einem Belegt-Token versehen, wie aufgrund der angeforderten Paketlängen vollständig belegt werden können und erst im folgenden Rahmen ein Frei-Token gesendet.The free tokens and the occupied tokens are from one generated specific station of the transmission system, which evaluates the tokens contained in a frame considered. If the transmission capacity requested by these tokens is smaller than the maximum available in one frame, a free token is sent in the following frame. If the sum of the packet lengths defined by the tokens sent out in a particular frame is greater than the length of one or more frames, as many consecutive frames are provided with an occupied token as can be completely occupied due to the requested packet lengths and only in the following frame sent a free token.
Das erfindungsgemäße Verfahren wird nachstehend anhand in den Figuren dargestellter Beispiele erläutert.The method according to the invention is explained below with reference to examples shown in the figures.
Es zeigt:
- Fig. 1
- den Aufbau eines Zeitrahmens für ausschließlichen Paket-Betrieb;
- Fig. 2
- den Aufbau eines Zeitrahmens für Paket- und Festkanalbetrieb;
- Fig. 3
- ein erstes Beispiel für Zugriffe auf den Übertragungsweg und die Belegung der Kanäle; und
- Fig. 4
- ein zweites Beispiel für Zugriffe auf den Übertragungsweg und die Belegung der Kanäle.
- Fig. 1
- the establishment of a time frame for exclusive package operations;
- Fig. 2
- the establishment of a time frame for packet and fixed channel operations;
- Fig. 3
- a first example of access to the transmission path and the assignment of the channels; and
- Fig. 4
- a second example of access to the transmission path and the assignment of the channels.
Der in Fig. 1 schematisch dargestellte Zeitrahmen enthält 1088 Kanäle mit einer Länge von 1088 Byte. Von diesen stehen 992 Kanäle für die Übertragung von Informationen zur Verfügung und die restlichen 96 Kanäle sind Signalisierkanäle. Die ersten 32 Signalisierkanäle bilden den sogenannten Systemsteuerblock SCB, in dem die für den Betrieb des Nachrichtenübertragungssystems notwendigen Steuerinformationen übertragen werden. Weitere vier Kanäle bilden einen sogenannten Token-Steuerblock TCB, von denen der erste Kanal entweder einen Belegt-Token oder einen Frei-Token enthält. Die anderen drei Kanäle dienen als Laufzeitausgleich. Die restlichen 60 Kanäle bilden einen sogenannten Token-Block TB. Ein Token besitzt eine Länge von 2 Byte und besteht aus einer Prioritätszahl PZ und einer Paketlängenzahl PL. Die Paketlänge wird in Einheiten von 4 Byte angegeben.The time frame shown schematically in FIG. 1 contains 1088 channels with a length of 1088 bytes. Of these, 992 channels are available for the transmission of information and the remaining 96 channels are signaling channels. The first 32 signaling channels form the so-called system control block SCB, in which the control information necessary for the operation of the message transmission system is transmitted. A further four channels form a so-called token control block TCB, of which the first channel contains either an occupied token or a free token. The other three channels serve as runtime compensation. The remaining 60 channels form a so-called token block TB. A token has a length of 2 bytes and consists of a priority number PZ and a packet length number PL. The packet length is specified in units of 4 bytes.
Fig. 2 zeigt einen Zeitrahmen, dessen Kanäle teilweise für Festkanalbetrieb reserviert und teilweise für Paket-Betrieb vorgesehen sind. Er enthält ebenfalls den Systemsteuerblock SCB, den Token-Steuerblock TCB und den Token-Block. Da die Anzahl der für Paket-Betrieb vorgesehenen Kanäle geringer ist als im Beispiel nach Fig. 1, sind auch nur entsprechend weniger Signalisierkanäle, nämlich 28 für den Token-Block vorgesehen.2 shows a time frame, the channels of which are partially reserved for fixed-channel operation and partially intended for packet operation. It also contains the system control block SCB, the token control block TCB and the token block. Since the number of channels provided for packet operation is smaller than in the example according to FIG. 1, only correspondingly fewer signaling channels, namely 28, are provided for the token block.
Jeder Station des Übertragungssystems ist ein bestimmter Token-Platz und eine bestimmte Prioritätszahl zugewiesen. Die Vergabe der Prioritätszahlen und der Token-Plätze erfolgt so, daß an die Stationen, denen derselbe Token-Platz zugewiesen, unterschiedliche Prioritätszahlen vergeben sind. Die den Stationen zugewiesenen Prioritätszahlen können gleich sein, sofern den Stationen unterschiedliche Token-Plätze zugeteilt wurden. Die einem Token einer Station zukommende Priorität hängt von der Prioritätszahl und dem der Station zugeordneten Token-Platz ab.Each station of the transmission system is assigned a specific token location and a specific priority number. The priority numbers and token places are assigned so that different priority numbers are assigned to the stations to which the same token place is assigned. The priority numbers assigned to the stations can be the same if the stations have been assigned different token places. The priority assigned to a token of a station depends on the priority number and the token space assigned to the station.
Eine bestimmte Station des Übertragungssystems geniert die Belegt- und die Frei-Token in Abhängigkeit von der Summe aller zu übertragenden Pakete. Ein Frei-Token in einem Rahmen N signalisiert den Stationen, daß im folgenden Token-Block des Rahmens N Token gesendet werden können. Ein Belegt-Token zeigt an, daß in dem betrachteten Rahmen kein Token-Block vorhanden ist, sondern alle Kanäle für die Informationsübertragung belegt sind. Die bestimmte Station zählt alle im Rahmen N vorhandenen Paketlängenzahlen zusammen. Aus der Summe aller Paketlängenzahlen ergibt sich die Anzahl von Rahmen, in denen sie ein Belegt-Token aussenden muß. Ist die Summe aller Paketlängen kleiner als 992 Byte, sendet sie im folgenden Rahmen N+1 ein Frei-Token aus.A certain station of the transmission system generates the busy and free tokens depending on the Sum of all packets to be transferred. A free token in a frame N signals to the stations that N tokens can be sent in the following token block of the frame. An occupied token indicates that there is no token block in the frame under consideration, but that all channels are used for the information transmission. The particular station adds up all the packet length numbers available in frame N. The sum of all packet length numbers results in the number of frames in which it must send out an occupied token. If the sum of all packet lengths is less than 992 bytes, it sends out a free token in the following frame N + 1.
Möchte eine Station eine Nachricht übertragen, sucht sie nach einem Frei-Token im Token-Steuerblock. Nach Erkennen eines Frei-Token schreibt sie ihre Prioritätszahl und die Paketlänge der zu übertragenden Nachricht in den ihr zugewiesenen Token-Platz ein. Sollten andere Stationen dem gleichen Token-Platz zugeordnet sein, kann sich auf diesem Token-Platz bereits ein Token befinden. Besitzt der Token der betrachteten Station eine höhere prioritätszahl als der Token der anderen Station, so überschreibt die betrachtete Station den anderen Token. Andernfalls wartet sie den nächsten Zeitrahmen ab. Anschließend kontrolliert die betrachtete Station, ob ihr Token von einer dritten Station überschrieben wurde. Findet sie ihren Token im Token-Block wieder, erhält sie Zugriff auf den Übertragungsweg.If a station wants to transmit a message, it looks for a free token in the token control block. After recognizing a free token, it writes its priority number and the packet length of the message to be transmitted in the token space assigned to it. If other stations are assigned to the same token location, a token can already be located on this token location. If the token of the station in question has a higher priority number than the token of the other station, the station in question overwrites the other token. Otherwise, it waits for the next time frame. The station in question then checks whether its token has been overwritten by a third station. If it finds its token in the token block, it gets access to the transmission path.
Sollte eine Station keinen Zugriff auf den Übertragungsweg erhalten haben, weil eine andere Station ihren Token überschrieben hat, erhöht sie ihre Prioritätszahl um einen bestimmten Betrag und sendet ihren neuen Token in einem der folgenden Rahmen aus. Der Betrag der Erhöhung ist im einfachsten Fall gleich der Anzahl der Stationen, die den gleichen Token-Platz zugewiesen bekommen haben. Durch die Höhe des Betrages und wegen der Zuordnung eines bestimmten Token-Platzes kann jede Station ihre Zugriffszeit deterministisch berechnen. Nach dem Erhalt des Zugriffs wird die Prioritätszahl wieder auf ihren ursprünglichen Wert zurückgesetzt.If a station has not received access to the transmission path because another station has overwritten its token, it increases its priority number by a certain amount and sends out its new token in one of the following frames. The amount of the increase is in the simplest case equal to the number of stations that have been allocated the same token space. Due to the amount and the allocation of a certain token space, each station can determine its access time deterministically. After receiving access, the priority number is reset to its original value.
Hat eine Station Zugriff auf den Übertragungsweg erhalten, kann sie ihr Paket in einem der nächsten Zeitrahmen aussenden. Den Startpunkt für diese Aussendung ermittelt die Station aus den im Token-Block angegebenen Paketlängen der Pakete, die von Stationen mit einem vor dem eigenen liegenden Token-Platz stammen.If a station has access to the transmission path, it can send out its packet in one of the next time frames. The station determines the starting point for this transmission from the packet lengths of the packets specified in the token block, which come from stations with a token slot located in front of its own.
Ein Paket setzt sich aus einem Header, der eigentlichen Information und Datensicherungsbits zusammen. Der Header beginnt mit einem Startwort und enthält die Empfänger- und Absenderadresse sowie die Länge der im Paket vorhandenen Information.A package consists of a header, the actual information and data backup bits. The header begins with a start word and contains the recipient and sender address as well as the length of the information contained in the package.
Fig. 3A zeigt einen Zeitrahmen N gemäß Fig. 1, dessen Token-Steuerblock ein Frei-Token und dessen Token-Block auf dem vierten, fünften, elften und dreißigsten Token-Platz einen Token enthält. Die Station mit dem Token-Platz 4 hat die Prioritätszahl 10 und die Paketlängenzahl 74 angegeben. Diese Station hat also 74 x 4 Bytes zu übertragen. Die Gesamtanzahl der in diesem Beispiel zu übertragenden Informationen beträgt 656 Byte. Da die Summe aller Paktelängen die im nächsten Rahmen N+1 zur Verfügung stehenden 992 Byte nicht überschreitet, wird im nächsten Rahmen im Token-Steuerblock wieder ein Frei-Token gesendet und ein Token-Block vorgesehen. Wie aus Fig. 3b ersichtlich, beginnt die Übertragung des ersten Paketes im ersten Kanal nach dem Token-Block. Die anderen Pakete schließen sich unmittelbar an die vorhergehenden Pakete an. Der Rest des Rahmens N+1 ist nicht belegt.FIG. 3A shows a time frame N according to FIG. 1, the token control block of which contains a free token and the token block of which contains a token at the fourth, fifth, eleventh and thirtieth token positions. The station with the
Fig. 4a zeigt genau wie auch Fig. 3a ein Beispiel eines Zeitrahmens N, der einen Frei-Token im Token-Steuerblock und vier Token auf vier Token-Plätzen im Token-Block enthält. Allerdings ist hier die Summe aller Paketlängen mit 1800 Byte größer als die in einem Rahmen übertragbaren 992 Byte. Daher weist der Rahmen N+1 nach dem Systemsteuerblock ein Belegt-Token auf. Der Rahmen N+1 enthält keinen Token-Block. Direkt nach dem Belegt-Token beginnt das erste Paket, an das sich nahtlos das zweite Paket anschließt (Fig. 4b). Der Teil des zweiten Paketes, der im Rahmen N+1 keinen Platz mehr findet, wird im Rahmen N+2 übertragen. An das zweite Paket schließt sich das dritte und vierte Paket an. Da der Rahmen N+2 nicht voll belegt ist, enthält er einen Frei-Token und einen Token-Block (Fig. 4c). Da im Token-Block des Rahmens N+2 kein Token enthalten ist, wird im Rahmen N+3 (Fig. 4d) überhaupt keine Information übertragen.FIG. 4a shows, just like FIG. 3a, an example of a time frame N which contains a free token in the token control block and four tokens on four token locations in the token block. However, the sum of all packet lengths of 1800 bytes is larger than the 992 bytes that can be transmitted in one frame. Therefore, the frame N + 1 has a busy token after the system control block. The frame N + 1 does not contain a token block. The first packet begins immediately after the busy token, followed by the second packet (FIG. 4b). The part of the second packet that no longer finds space in frame N + 1 is transmitted in frame N + 2. The third and fourth packages follow the second package. Since frame N + 2 is not fully occupied, it contains a free token and a token block (FIG. 4c). Since no token is contained in the token block of frame N + 2, no information is transmitted at all in frame N + 3 (FIG. 4d).
Beim Empfangen vergleicht jede Station die im Header der Pakete enthaltene Empfängeradresse mit ihrer eigenen Adresse. Bei Übereinstimmung der Adressen speichert die Station das Paket in einem Empfangsspeicher. Die Länge des Pakets entnimmt sie dem Header und kann dadurch das Ende des Pakets und den Anfang des nächsten Pakets genau bestimmen.When receiving, each station compares the recipient address contained in the header of the packets with its own address. If the addresses match, the station stores the packet in a receive memory. The length of the packet is taken from the header and can thereby determine the end of the packet and the beginning of the next packet.
Die Verteilung der Zeitschlitze auf Festkanäle und für die Übertragung von Paketen verwendete Kanäle wird abhängig von der jeweils benötigten Übertragungskapazität gesteuert. Entsprechende Steuerinformationen werden im Systemsteuerblock übertragen. Dabei können auch die Zeitschlitze eines Zeitrahmens in mehrere sogenannte Unterrahmen aufgeteilt werden, die je einen eigenen Token-Steuerblock, Token-Block und eine bestimmte Anzahl von Zeitschlitzen zur Informationsübertragung enthalten und verschiedenen Gruppen von Stationen zugeordnet sind. Dadurch ist auch bei starker Auslastung des Übertragungsweges eine Reservierung von Übertragungskapazität für einzelne Gruppen von Stationen möglich.The distribution of the time slots on fixed channels and channels used for the transmission of packets depends on the transmission capacity required in each case controlled. Corresponding control information is transmitted in the system control block. The time slots of a time frame can also be divided into several so-called subframes, each of which contains its own token control block, token block and a certain number of time slots for information transmission and are assigned to different groups of stations. This makes it possible to reserve transmission capacity for individual groups of stations even when the transmission path is heavily loaded.
Claims (8)
dadurch gekennzeichnet, daß jeder Token zusätzlich eine Paketlängenzahl (PL) enthält, welche die Länge des zu übertragenden Pakets angibt, und daß jede Station aus den Angaben der in den Signalisierkanälen enthaltenen Token den Startpunkt für die Aussendung ihres Pakets in einem der folgenden Zeitrahmen ermittelt, indem die Station die Summe aller Paketlängen bildet, die in den Token angegeben sind, die sich auf einem im Zeitrahmen vor dem eigenen liegenden Token-Platz befinden.Method for controlled access to time-division multiplex channels of a transmission system by means of tokens, the transmission system containing a plurality of stations accessing a transmission path, of which one station specifies a time frame, the time slots of which are partly as fixed channels and partly for the transmission of packets (bursts ) and the remaining time slots are used as signaling channels, in which each station that wants to send a packet first sends a token in a signaling channel and only sends out the packet when this token is subsequently received in the signaling channel, the order in which the stations access received on the channels used for packet operation, depends on a priority number (PZ) contained in the token,
characterized in that each token additionally contains a packet length number (PL) which indicates the length of the packet to be transmitted, and in that each station determines the starting point for the transmission of its packet in one of the following time frames from the details of the tokens contained in the signaling channels, by the station forming the sum of all packet lengths that are specified in the tokens that are on a token place that lies in the time frame in front of the own.
dadurch gekennzeichnet, daß jede Station die Prioritätszahl ihres Tokens um einen bestimmten Wert erhöht, wenn sie nach Aussendung ihres Tokens diesen Token nicht in dem betreffenden Signalisierkanal empfängt, und danach ihren Token mit der erhöhten Prioritätszahl erneut auf dem Signalisierkanal aussendet.Method according to claim 1,
characterized in that each station increases the priority number of its token by a certain value if, after sending its token, it does not receive this token in the relevant signaling channel, and thereafter retransmits its token with the increased priority number on the signaling channel.
dadurch gekennzeichnet, daß der Wert der Erhöhung der Prioritätszahl gleich der Anzahl der Stationen ist.Method according to claim 2,
characterized in that the value of increasing the priority number is equal to the number of stations.
dadurch gekennzeichnet, daß jede Station nach dem Zugriff auf den Übertragungsweg ihre Prioritätszahl wieder auf ihren ursprünglichen Wert zurücksetzt.Method according to claim 2 or 3,
characterized in that after accessing the transmission path, each station resets its priority number to its original value.
dadurch gekennzeichnet, daS die bestimmbare Station die Summe der Paketlängen der in einem Rahmen ausgesendeten Token aller Stationen ermittelt, und dann, wenn die Summe der Paketlängen die Länge eines oder mehrerer Rahmen übersteigt, in einem oder mehreren aufeinanderfolgenden Rahmen einen Belegt-Token sendet, und erst in demjenigen Rahmen einen Frei-Token sendet, der nicht mehr ganz belegt ist.Method according to claim 5,
characterized in that the determinable station determines the sum of the packet lengths of the tokens sent out in one frame of all stations, and then sends an occupied token in one or more successive frames if the sum of the packet lengths exceeds the length of one or more frames, and only sends a free token in the frame that is no longer fully used.
dadurch gekennzeichnet, daß die Zeitschlitze eines Zeitrahmens in mehrere, verschiedenen Gruppen von Stationen zugeordnete Unterrahmen aufgeteilt werden.Method according to claim 7,
characterized in that the time slots of a time frame are divided into several subframes assigned to different groups of stations.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4040248 | 1990-12-17 | ||
| DE19904040248 DE4040248C1 (en) | 1990-12-17 | 1990-12-17 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0491202A2 true EP0491202A2 (en) | 1992-06-24 |
| EP0491202A3 EP0491202A3 (en) | 1994-06-22 |
Family
ID=6420504
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19910120531 Withdrawn EP0491202A3 (en) | 1990-12-17 | 1991-11-29 | Access method |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0491202A3 (en) |
| DE (1) | DE4040248C1 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO1996017453A2 (en) * | 1994-12-01 | 1996-06-06 | Philips Electronics N.V. | A communication system, a private automatic branch exchange, and a line card |
| WO1998023066A1 (en) * | 1996-11-15 | 1998-05-28 | Philips Electronics N.V. | Communication network with quality of service |
| WO2005053246A2 (en) * | 2003-11-19 | 2005-06-09 | Honeywell International Inc. | Voting mechanism for transmission schedule enforcement in a hub-based tdma network |
| WO2005053245A2 (en) * | 2003-11-19 | 2005-06-09 | Honeywell International Inc. | Arbitrating access to a timeslot based on a priority scheme in a tdma network with asynchronous hub |
| US7668204B2 (en) | 2003-11-19 | 2010-02-23 | Honeywell International Inc. | Port driven authentication in a network |
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| US4500987A (en) * | 1981-11-24 | 1985-02-19 | Nippon Electric Co., Ltd. | Loop transmission system |
| EP0115883A2 (en) * | 1983-01-10 | 1984-08-15 | Philips Patentverwaltung GmbH | Method of controlling the access to a TDM communication channel |
| EP0122765A2 (en) * | 1983-04-14 | 1984-10-24 | AT&T Corp. | Network protocol for integrating synchronous and asynchronous traffic on a common serial data bus |
| EP0212701A1 (en) * | 1985-07-15 | 1987-03-04 | Koninklijke Philips Electronics N.V. | Method of getting access to and utilizing a message channel in a communication system and arrangement for performing the method |
| EP0391792A1 (en) * | 1989-04-03 | 1990-10-10 | Js Telecom | Method and device for accessing a communication medium shared between users transmitting with different priority levels in a circuit or packet mode |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996017453A2 (en) * | 1994-12-01 | 1996-06-06 | Philips Electronics N.V. | A communication system, a private automatic branch exchange, and a line card |
| WO1996017453A3 (en) * | 1994-12-01 | 1996-08-08 | Philips Electronics Nv | A communication system, a private automatic branch exchange, and a line card |
| US5812548A (en) * | 1994-12-01 | 1998-09-22 | U.S. Philips Corporation | Communication system, a private automatic branch exchange, and a line card |
| WO1998023066A1 (en) * | 1996-11-15 | 1998-05-28 | Philips Electronics N.V. | Communication network with quality of service |
| US6418477B1 (en) | 1996-11-15 | 2002-07-09 | Philips Electronics North America Corporation | Communication network |
| WO2005053246A2 (en) * | 2003-11-19 | 2005-06-09 | Honeywell International Inc. | Voting mechanism for transmission schedule enforcement in a hub-based tdma network |
| WO2005053245A2 (en) * | 2003-11-19 | 2005-06-09 | Honeywell International Inc. | Arbitrating access to a timeslot based on a priority scheme in a tdma network with asynchronous hub |
| WO2005053246A3 (en) * | 2003-11-19 | 2005-07-28 | Honeywell Int Inc | Voting mechanism for transmission schedule enforcement in a hub-based tdma network |
| WO2005053245A3 (en) * | 2003-11-19 | 2005-09-15 | Honeywell Int Inc | Arbitrating access to a timeslot based on a priority scheme in a tdma network with asynchronous hub |
| US7630390B2 (en) | 2003-11-19 | 2009-12-08 | Honeywell International Inc. | Asynchronous hub |
| US7668204B2 (en) | 2003-11-19 | 2010-02-23 | Honeywell International Inc. | Port driven authentication in a network |
| US7873739B2 (en) | 2003-11-19 | 2011-01-18 | Honeywell International Inc. | Voting mechanism for transmission schedule enforcement |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0491202A3 (en) | 1994-06-22 |
| DE4040248C1 (en) | 1991-12-19 |
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